In the course of Release 11 standardisation, signalling support for conveying assistance information from a user equipment (UE) is being discussed for multimedia broadcast-multicast service (MBMS), in-device coexistence (IDC) and enhancements for diverse data applications (EDDA). While the information needed to assist the network in case of MBMS, IDC and EDDA differ in nature, it would be beneficial to have a common framework for the reporting. Moreover, there may be such features in the future that the evolved NodeB (eNB) requires some assistance information from UE. Thus the same framework as in the present application can be used in such cases.
One of the problems related to the handling of assistance information is that the UE needs to know whether the eNB supports the signalling. Further, at handover, the overhead needs to be minimized. Another problem in this regard is that mobility across eNBs of different releases or having different set of functionalities must be supported.
In this regard, in order to reduce overhead, in high speed uplink packet access (HSUPA), for the Scheduling Information (needed to assist the eNB in making scheduling decisions), it has been specified for the UE that if an enhanced dedicated channel (E-DCH) serving cell change occurs and if the new E-DCH serving cell was not part of the previous Serving E-DCH radio link set (RLS), the transmission of a Scheduling Information shall be triggered on that frequency, as described in document [1].
In order to let the UE know whether the eNB supports the signalling, it has been proposed to add signalling to let the UE know whether assistance information are needed, but without addressing the mobility issue, as described in document [2].
For mobility, it has been proposed that the UE should follow an order given by the target cell whether to report the assistance information after handover or not, as described in document [3]. Further, the options of UE receiving the confirmation of [assistance-information] context transfer from a target cell, and of UE always reporting assistance information after handover have been discussed in document [4].
Moreover, for proximity indication, proximity reporting of CSG cells is enabled by network (NW) dedicated configuration to the UE (otherConfig in RRC specification[5]). UE will only report proximity of closed subscriber group (CSG) cells if configured by the NW. Proximity status is not transferred between cells and thus UE needs retransmit proximity at cell change if UE still considers proximity being valid.